NSW in December 2013: Dry end to the year

Rainfall - Driest December since 2001

NSW recorded a statewide average rainfall of 23.3 mm during December 2013, which is less than half the historical average of 53.8 mm and the driest December since 2001. Most of the state recorded below average rainfall, with the exception of parts of the Victorian border, with much of the northeast recording rainfall in the driest 10% of years. The Murray Darling Basin also recorded 21.3 mm of rain, the driest December since 2001.

There were few significant rain events during the month. A cold front and surface trough crossed the state on the 5th and 6th, with widespread thunderstorm activity across the state and locally heavy falls along the Victorian border. On the 17th, thunderstorm activity across the Northern and Central Tablelands also caused locally heavy falls, with a daily total of 81 mm recorded at Emmaville. Finally, a surface trough produced rain as it crossed the state on Christmas Day and Boxing Day, with falls of up to 71.6 mm at Bellambi to 9 am on the 26th.

Temperature - Hot and cold records broken

The statewide average maximum temperature during December 2013 was 1.6 °C above the historical average, with most of the state recording temperatures between 1 °C and 2 °C above average, warmest in the southwest. The statewide average minimum temperature was 0.5 °C above average, with most of the state within 1 °C of normal, warmest in the southwest. The mean temperature was consequently 1.1 °C above the historical average.

A warm start to the month was followed by very cold temperatures on the 5th, which was the coldest December day on record for Cobar and Bombala. Cold conditions persisted until the 7th, with several stations also recording record cold nights on the 6th and 7th including Hay and Scone. This was followed by generally mild conditions until a heatwave began to emerge on the 18th.

Both maximum and minimum temperatures in southern NSW were more than 10 °C above average on the 19th and 20th, with warm temperatures extending northward on subsequent days. Broken Hill Airport recorded four consecutive days above 40 °C between the 18th and 21st, only the second such spell on record for December, while several stations in the central tablelands including Orange and Katoomba recorded their warmest night on record on the 23rd.

Cooler temperatures were associated with a trough over the 24th and 25th before a warm end to the year, with particularly warm temperatures across the state on the 28th and 29th. Maximum temperatures reached 46.2 °C at Mungindi on the 29th, its warmest December day on record, with records also broken at Inverell and Glen Innes.

Notes

A Monthly Climate Summary is prepared to list the main features of the weather in New South Wales using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at
9 am on Monday 6 January 2014.
Some checks have been made on the data, but it is possible that results will change
as new information becomes available.

Averages are long-term means based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median
is sometimes more representative than the
mean
of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
decile ranking
(very low rainfall is in decile 1, low in decile 2 or 3,
average in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a
percentage of the long-term mean.

The ACORN-SAT dataset
is being used for temperature area averages from December 2012 onwards.
The major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, rather than 1950,
and hence rankings are calculated using a larger set of years.